Black soybean (Glycine max (L.) Merr), a type of soybean with a black seed coat, has long been used as a health food and herb in Chinese traditional medicine, and the medicinal effects therefore have been studied for years. Some Chinese medical codices have disclosed that the black bean could be provided as detoxifier, anti-inflammatory drug and blood nutrient.
Specifically, black soybean phytochemicals inhibited the growth of transplantable human bladder carcinoma and tumor angiogenesis in mice (Zhou J R et al., Cancer Res. 58(22):5231-81999, 1998); and black soybean, displaying an antioxidant activity, reduced low density lipoprotein oxidation, which might play a crucial role in the prevention of oxidation-relative diseases (Takahashi. R et al, J Agric Food Chem., 53(11):4578-82, 2005).
Retinal pigment epithelium (RPE) is a monolayer cell at the surface layer of the retina, which are located between the Bruch's membrane and the photoreceptors. The villous processes at the top of RPE are connected to the outer segments of the photoreceptors, and the basal infoldings at the bottom of RPE are connected to the choroids via the Bruch' membrane. Since the RPE can effectively remove or transmit the toxic materials and the metabolite of the choroid coat and the retina, the RPE form a blood-retinal barrier. In addition, the RPE has many functions, such as receiving light, phagocytizing the outer segments separated from the rod cell and the cone cell because of light stimulation, catabolizing the phagosome, synthesizing the extracellular matrix and the melanin, detoxifying the medicine, providing the essential material for reproducing the outer segments of the photoreceptor, storing and transmitting the Vitamin A, synthesizing the rhodospin, and forming the adherent force of the retina (Wenzel et al., Progress in Retinal and Eye Research 24: 275-306, 2005).
According to the statistics, a RPE of rat could remove 25000 outer segments separated from the rod cells and the cone cells because of light stimulation in one day, which obviously showed the importance of the frequent phagocytic metabolism (Mayerson and Hall, The Journal of Cell Biology, 103:299-308, 1986). The normal phagocytosis of the RPE plays a critical role in maintaining the health of the photoreceptors in the retina. Once the phagocytic ability of RPE is decreased, it will result in the degeneration of the photoreceptors (Wenzel et al., Progress in Retinal and Eye Research 24: 275-306, 2005). Therefore, to maintain the RPE function is quite important for the visional system. So far, there is no good treatment of a disease/disorder associated with RPE disturbance.